The present invention generally relates to wireless communication networks, and particularly relates to managing packet data connections in such networks.
With the change-over to an emphasis on packetized data services, current and planned wireless communication networks include mobility management features that enable packet data connections with mobile stations to be maintained as the mobile stations move within and between the networks. For example, in current and planned iterations of cdma2000 wireless networks, the so-called “packet core network” provides packet-data-based registration, roaming, and forwarding services for mobile stations using Internet Protocol (IP) centric routing. Various other existent or planned wireless network standards, such as Wideband CDMA, provide similar packet data routing capabilities.
The typical cdma2000 network is subdivided into so-called “packet zones,” with each zone served by a unique combination of a Packet Data Serving Node (PDSN) and a Packet Control Function (PCF). Each PCF typically is associated with one or more Base Stations (BSs), thus the “packet zone” coverage of each PCF “maps” to the radio coverage of its associated BSs. Each PDSN may support one, or many PCFs, and the typical network may include any number of PDSNs. Regardless, when providing packet data connectivity between the network and a given mobile station, the network establishes a Point-to-Point Protocol (PPP) connection to the mobile station, with one end of the PPP link logically anchored at a selected one of the PDSNs, and with the other end logically anchored at the connected mobile station.
When a mobile station with an active packet data call undergoes an inter-BS hard handoff (HHO), it is often the case that the mobile station also has traversed a packet zone boundary, which is referred to as an inter-BS/inter-PCF HHO. In such cases, the target BS must set up connections to a new PCF and, in some cases, to a new Packet Data Serving Node (PDSN).
If the HHO was to a different PDSN, the underlying mobility event has changed the Foreign Network association of the mobile station, since each PDSN emulates a different Foreign Agent within the Mobile IP network infrastructure. With the Foreign Agent change, the target PDSN is required to perform PPP re-negotiation and carry out Agent Advertisement procedures to update the associated bindings. Such procedures generally comprise updating the mobile station's “care of” address, and typically involve Agent Discovery processing based on the exchange of Agent Advertisement and Agent Solicitation messages.
Thus, inter-PDSN mobile station handoffs require PPP re-negotiations and Foreign Agent Advertisement procedures. Conversely, intra-PDSN mobile station handoffs typically do not require link re-negotiation and agent advertisement procedures, because the mobile station remains under the care of the same PDSN, i.e., the target BS/PCF and source BS/PCF are under the same PDSN. These general requirements apply both to HHO (active connection) and “dormant” handoff (DHO), where the mobile station's data connection is not being used. Recognizing the handoff cases that require PPP link re-negotiation and agent advertisements versus those that do not is aided by the use of packet zone tracking variables, which allow PDSNs to track the prior and current packet zone locations of a mobile station undergoing a mobility event, i.e., undergoing some type of handoff.
For example, “Interoperability Specification (IOS) for cdma2000 Access Network Interfaces—Part 3 Features,” released as 3GPP2 A.S0013-A by the 3rd Generation Partnership Project 2 (3GGP2), sets forth the use of “Previous Access Network Identifiers” or PANIDs and “Current Access Network Identifiers” or CANIDs, in the context of packet data link mobility management. Each PCF in a given network is uniquely identified by an Access Network Identifier (ANID), which may comprise a combination of Packet Zone Identifier (PZID), Network Identifier (NID), and System Identifier (SID). Thus, PANID and CANID information can be used to track movement of mobile stations between packet zones of the network.
In general terms, when a PDSN receives a registration message for a given mobile station, which happens for new call setups and for mobility events, for example, it determines whether it has an established packet data connection for that particular mobile station. If not, the PDSN establishes a connection for the mobile station. If a previous connection exists, the PDSN still will perform re-negotiation of the connection and carry out Foreign Agent Advertisement if it cannot verify that the mobile station has not moved out of, and then back into, the PDSN's coverage area without detection by the PDSN. Such checks are based on comparing PANID information received in the registration message with PANID information stored at the PDSN for the mobile station's existing connection.
If mismatching PANID information is received, or if no PANID information is received, the PDSN assumes that re-negotiation of the connection and agent advertisements are needed, and thus carries out such processing. To the extent that PANID mismatches at the PDSN can occur in circumstances where the mobile station remained under the same PDSN, but underwent one or more particular combinations of intra-PDSN hard and dormant handoffs, such re-negotiations and agent advertisements represent unnecessary signaling and processing overhead.
Mismatches may occur for a number of reasons. In particular, in existing networks, PDSN's typically store PANID information for each mobile station's packet data connection, and update that stored PANID responsive to packet zone movement of the mobile stations, irrespective of whether that movement arises in the context of dormant or hard handoffs. Conversely, the PANID information stored at mobile stations typically is updated during dormant handoff events, but is not updated during hard handoffs.
Specifically, a dormant mobile station monitors one or more broadcast or overhead channels transmitted in each radio sector or Access Network coverage area to identify its current packet zone location. Thus, a dormant mobile station recognizes that it has undergone dormant handoff between packet zones by periodically comparing the ANID information being broadcast with its stored PANID information. Upon detecting a mismatch, the dormant mobile station sends an Origination Message or other notification to the network to trigger packet data re-registration, and it updates its stored PANID information to reflect its current location. The PDSN typically updates its stored PANID for the mobile station as part of this dormant re-registration process.
However, mobile stations typically do not monitor these broadcast channels when they are in an active packet data call. Thus, the PANID information stored by a given mobile station becomes “out of date” or “stale” when it moves between packet zones during hard handoff. Indeed, the conventional mobile station typically holds the PANID value of the location where the call was first established, regardless of the number of subsequent hard handoffs it undergoes during that call, and updates that information only after the call ends and it goes dormant.
Simply put, the conventional PDSN updates its stored tracking variables for both hard and dormant handoffs of mobile stations, and typical mobile stations update their stored tracking variables during dormant but not hard handoffs. Thus, the PDSN-stored PANID information can become “unsynchronized” with the mobile-stored PANID information in cases where a mobile station having an established data connection at a given PDSN undergoes a combination of hard and dormant handoffs under that PDSN.